From the related art, signature analysis is known as a method for compressing data, which is based on the so-called CRC (cyclical redundancy check) method. As a function of the data to be transmitted, a resulting data word is formed according to a specifiable signature formation method, which constitutes the signature and characterizes the compressed data stream. The likelihood that a correct signature is formed in spite of faults in the data stream is very low and decreases with the data capacity of the signature word. Signatures are used, for example, for securing data transmissions, for monitoring read-only memories in computers and for identifying data streams such as for example of digital hardware signals in the context of testing circuits or data contained in a document. For the related art, reference is made to Abramovici, Miron, et al.: Digital Systems Testing and Testable Design, New York, IEEE Press, 1990.
In hardware, the signature is usually formed sequentially bit by bit with the aid of a linear feedback shift register (LFSR). It is known to implement this sequential signature analysis method in software as well. This method, however, is either very slow due to the sequential method of operation or it requires a relatively high amount of memory space for tables (so-called lookup tables) in order to shorten the computing time. Regarding the related art of such software-implemented sequential methods for signature analysis, reference is made to Williams, R. N.: A Painless Guide to CRC Error Detection Algorithms, Version 3, Aug. 19, 1993, Rocksoft Pty Ltd., Hazelwood Park 5066, Australia, ftp://ftp.rocksoft.com/Qapers/crc v3.txt.
Furthermore, a method for signature formation using a parallel method of operation (data word by data word) is known. This known method operates for example with the aid of a signature register having multiple inputs (MISR, multiple input shift register). The parallel method of operation, for example, allows for 32 bit input data to be processed in one step using a 32 bit processor. A method of this kind is known, for example, from U.S. Pat. No. 5,938,784.
Especially for safety applications in a motor vehicle such as, for example, steer-by-wire or autonomous driving, fault-tolerant and therefore redundant electronic systems are used that have a high demand for secure data exchange between systems, control units, computers and/or processing units. This communication can occur on three levels of communication. A system communication between two or more control units occurs, for example, via a bus system such as, for example, CAN (controller area network), TTCAN (time triggered CAN), FlexRay or TTP/C (time triggered protocol class C). A control unit-control unit communication or a computer-computer communication involving two control units or computers occurs via interfaces such as, for example, RS232, RS422, SPI (serial peripheral interface) or SCI (serial communications interface). A processing unit-processing unit communication occurs within a control unit. Since in these systems, in addition to computing time, data communication time also represents a bottleneck, using the MISR method to safeguard the many data communications is especially advantageous. It reduces to a minimum the computing time required for safeguarding the data communication in the sender and in the receiver.
In the case of the known methods, it may happen—even if it is an extremely rare occurrence—that a faultless signature is formed in spite of faulty data within a message. That is to say that, although the data to be transmitted and the transmitted data do not match each other, the first signature formed via the data to be transmitted and the second signature formed via the transmitted data match nevertheless. This is known as fault masking.